Recent Discoveries: Did Cosmic Dust Doom the Dinosaurs?

A controversial study by researchers at the University of Florida and Carnegie Institution theorizes that
space dust in Earth's atmosphere and changes in the planet's orbit may have started the gradual extinction
of dinosaurs and other life thousands of years before a massive asteroid collision dealt the final blow.

Currently, Earth is accumulating about 30,000 metric tons of cosmic dust from interplanetary space each
year. The scientists found that most of this dust comes from just three families of asteroids (Eos, Themis,
and Koronis) in the solar system's asteroid belt. As Earth orbits the sun, it passes through this cloud of
dust particles, capturing some of the dust in its atmosphere. The study showed that the amount of dust
captured depends on the shape (ellipticity) and tilt (inclination) of the Earth's orbit. These vary periodically
due to the gravitational pull of other planets. The dust buildup rises and falls in about 100,000 periods that
correspond to ice-age cycles.

Space dust could remain at high levels in the atmosphere for periods of thousands of years, and any
associated cooling would also persist for this length of time. If the amount of dust in Earth's atmosphere
altered the climate, the change would cause gradual extinction.